1. Field of the Invention
The present invention relates to a hard disk drive. More particularly, the present invention relates to an actuator latch system of a hard disk drive, which locks an actuator of the hard disk drive in place when the disk of the hard disk drive is not rotating.
2. Description of the Related Art
Hard disk drives (HDD) are used in electronic devices such as computers to reproduce data from a disk or record data onto the disk. More specifically, in addition to such a disk, an HDD includes a magnetic (read/write) head, an actuator for moving the magnetic head over a desired location (track) of the disk, and a spindle motor for rotating the disk. The magnetic head is floated a predetermined height from the recording surface of the disk while the disk is rotated, and detects/modifies the magnetization of the recording surface of the disk to reproduce/record data from/onto the disk.
In addition, when the HDD is not in use, that is, when the disk is not rotating, the magnetic head is parked off of the recording surface of the disk. Systems for parking the magnetic head of the HDD include a contact start stop (CSS) type of parking system and a ramp type of parking system. In the CSS type of parking system, an inner circumferential portion of the disk devoid of recorded data is reserved as a parking zone, and the magnetic head is held against the parking zone of the disk when the magnetic head is parked. In the ramp type of parking system, a ramp is disposed radially outwardly of the disk, and the actuator is held against the ramp when the magnetic head is parked.
However, an HDD can be subjected to external shock or vibrations when the HDD is not in use. Such external shock or vibrations have the potential to move the magnetic head out of the parking zone or off of the ramp and onto the recording surface of the disk. If this were allowed to happen, the magnetic head or the recording surface of the disk could be damaged. Therefore, the actuator needs to be locked in place when the magnetic head is parked. To this end, HDDs include various kinds of actuator latch systems.
FIGS. 1A-1C and 2 illustrate a conventional latch system of an HDD for locking the actuator of the HDD in place when the magnetic head is parked.
Referring to FIG. 1A, the actuator 10 of the HDD includes a swing arm 12 that is rotatably supported by a pivot 11, a suspension 13 disposed on an end portion of the swing arm 12, a slider 14 supported by the suspension 13, and a voice coil motor (VCM) for rotating the swing arm 12 about the axis of pivot 11. The head slider 14 contains the magnetic head. The suspension biases the head slider 14 and hence, the magnetic head, toward a (recording) surface of the disk during a read/write operation in which the magnetic head is recording data onto the disk or reading data from the disk. The VCM includes a VCM coil 16 wound on a rear end portion of the swing arm 12, and a magnet 17 facing the VCM coil 16.
In addition, the HDD includes an inertial latch system 20 for locking the swing arm 12 of the actuator 10 in place when the magnetic head is parked on a ramp 19. The inertial latch system 20 includes a latch lever 21 supported so as to be rotatable about the axis of a pivot 22, and a member constituting an integral part of the swing arm 12 of the actuator 10 and delimiting a notch 26 at the rear end portion of the swing arm 12. The latch lever 21 has a latch hook 23 at a front end thereof, and a counterbalance 24 on rear end thereof. The hook 23 is received within the notch 26 so as to engage the swing arm 12 when the swing arm 12 rotates in one direction while the magnetic head is parked. The inertial latch system 20 also includes a retract ball 25 of a magnetic material installed on the counterbalance 24 such that a magnetic force of attraction is produced between the retract ball 25 and the magnet 17. The magnetic force of attraction generates torque which acts to bias the latch lever 21 in a clockwise direction about the axis of pivot 22.
The conventional inertial latch system 20 operates as follows.
Referring to FIG. 1B when shock applied to the HDD while the magnetic head is parked on the ramp 19 causes the swing arm 12 of the actuator 10 and the latch lever 21 to rotate counter-clockwise due to inertia, the latch hook 23 is received in the notch 26 such that the rotation of the swing arm 12 of the actuator 10 is arrested. On the other hand, when shock applied to the HDD while the magnetic head is parked on the ramp 19 causes the swing arm 12 and the latch lever 21 to rotate clockwise due to inertia, the rear end portion of the swing arm 12 and the counterbalance 24 of the latch lever 21 collide. As a result, the swing arm 12 and the latch lever 21 rebound and rotate counter-clockwise. Therefore, as described above, the latch hook 23 is received in the notch 26 such that the rotation of the swing arm 12 of the actuator 10 is arrested.
Next, referring to FIG. 1C, the magnetic head is moved from the ramp 19 to a location over a recording surface of the disk in order to conduct a read/write operation. To this end, the swing arm 12 is rotated counter-clockwise by the VCM. At the same time, the latch lever 21 is rotated clockwise by the magnetic force of attraction between the magnet 17 and the retract ball 25. Therefore, the hook 23 of the latch lever 21 does not interfere with the swing arm 12, i.e., the swing arm 12 can rotate freely in the counter-clockwise direction.
However, in this case, the swing arm 12 can be engaged by the hook 23 of the latch lever 21 if the speed at which the latch lever 21 rotates in the clockwise direction is slowed or otherwise becomes irregular. This problem will be described in more detail below.
Referring to FIG. 2, the pivot 22 is fixed on a base 30 of the HDD, the magnet 17 is mounted on a lower yoke 17a, and an upper yoke 17b extends over the pivot 22. In addition, a bottom surface of the latch lever 21 contacts an upper surface of a flange 22a of the pivot 22. Therefore, friction is created between the flange 22a of the pivot 22 and the latch lever 21 when the latch lever 21 rotates. Sometimes, the contacting surfaces of the latch lever 21 and the flange 22a are rough, or a burr or foreign substance may be present on the contacting surfaces. Also, the latch lever 21 and the upper yoke 17b contact each other if the HDD is used in a mobile electronic device while being turned upside-down. In these cases, the force of friction between the latch lever 21 and the flange 22a of the pivot 22 can be so great that the latch lever 21 does not rotate properly in the clockwise direction. Consequently, the latch system will not release the swing arm 12 when the swing arm 12 is rotated counter-clockwise by the VCM to begin a read/write operation.
Conventionally, protrusions are formed on the upper surface and the bottom surface of the latch lever in attempt to obviate the above-described problem. More specifically, the protrusions reduce the contact area and hence, the force of friction between the latch lever 21 and the flange 22a of the pivot 21. However, this technique does not always prevent the above-described problem from occurring.